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Home My WebLink AboutSWP272255(3) STORM DRAINAGE REPORT FOR RAYMOND AVENUE CENTER RENTON, WASHINGTON BY jo BUSH, ROED & HITCHINGS 2009 MINOR AVENUE EAST SEATTLE, WA 98102 (206) 323-4144 CONTACT : JOHN E . ANDERSON, P.E. FEB 15 1996 DEVELOPMENT BRH JOB NO. 92233 . 02 CITyOFRI°IV'roty G 1�rJ wpF s<r, c Is \ EXPIRES 12/1/97 i • I F( LONGACRES RACE TRACK z CIFIC S.W GL " \ T 40MAS AV 5.w. O RAYMOND AV S.W. cn 0 Z D (VALLEY FREEWAY) STATE SIGN ROUTE 167 • Raymond Avenue Center is a 10.39 acre site located at the southwest quadrant of the intersection of Southwest 19th Street and Raymond Avenue South. The proposed development would occur on Parcel B. Development would include the construction of a 99, 900 square foot building and associated parking. A divided driveway would be extended to Raymond Avenue . Spring Brook Creek defines the southern and western boundary of the site. The original easement for Spring Brook Creek did not coincide with the actual stream location. Bush, Roed & Hitchings has prepared a lot line adjustment which defines the easements according to the surveyed location of the stream. Lot lines shown on the documents submitted for site plan and shoreline review reflect the most current survey information. Several years ago, the site was filled to approximately elevation 18. Fill slopes toe down to the banks of Spring Brook Creek on the southern and western boundary. On the eastern boundary, the fill slopes toe down approximately 60 feet west of the east property line. Areas east of the fill slopes are classified wetlands. A 60 inch culvert discharges into a ditch on the west side of Raymond Avenue . The ditch is located within the 19th Street right-of-way just north of the north property line. Existing drainage maps indicate the area tributary to the ditch include Panther Creek Wetlands. From the 60 inch culvert, the ditch flows west to Spring Brook Creek. Existing grades on the developable areas are approximately 9 to 10 feet higher than surrounding grades . The ground surface where the proposed development will occur is flat. Tall grasses cover the area. There are no significant tree located within the buildable area . Storm water run-off from the site sheet flows to the surrounding low lands . No defined drainage courses were observed on the site . The proposed site plan maintains a minimum 50 foot setback from Spring Brook Creek and a 25 foot setback from the surrounding wetlands . In most areas the proposed development exceeds the minimum setback requirements . Storm water run-off from the developed areas south of the building will sheet flow across the asphaltic concrete paving to three curb breaks . From the curb breaks the storm water flows into biofiltration swales . Areas north of the building will sheet flow to catch basins . From the catch basins the storm water is tightlined to a biofiltration swale. According to the design standards, a single 200 foot long biofiltration Swale would be adequate. Using four, 200 foot long biofiltration swales will provide a significantly higher water quality than required by the design standards . A wetpond is required because the development is located next to Spring Brook Creek and has more than one acre of impervious surface area subject to vehicular traffic. Also, since the storm water will discharge into Spring Brook Creek the detention volume will be calculated using Department of Fisheries guidelines . These • standards require a peak discharge rate from the detention system equal to 1/2 the pre-developed 2 year rate for a 10 year developed storm inflow. Peak discharge rates from the detention system for storm events greater than the 10 year can match pre-developed peak rates for the same storm event . • Analysis of the combine wetpond/detention pond shows that it performs significantly better than the Department of Fisheries guidelines. Initial sizing was base on maximizing the available area. The goal was to make the detention volume shallow. This would prevent storm water from backing into the biofiltration swales . By making the detention volume shallow, there is not sufficient head pressure to reach the pre-developed 25 year and 100 year peak discharge rates . The calculations show the developed 25 year storm will be discharges at approximately 1/2 the pre- developed 10 year peak rate and the developed 100 year storm discharges at less than the pre-developed 10 year peak rate. Therefore, development of this site would reduce the peak rates for all storm events . Volume provided by the wetpond exceeds the required volume by approximately a factor of three. This is also a result of maximizing the available area. The design guidelines require a 3 foot minimum depth plus 1 foot of sediment storage. Maintaining the depth requirement across the pond provides a storage volume of approximately 26, 881 cubic feet . The required volume is approximately 8, 116 cubic feet. Therefore, the storm water quality will be significantly better than required by Department of Fisheries guidelines. The additional volume will also mitigate the • two small areas filled within the 100 year flood plain. A storage volume of 10, 024 cubic feet is required for compensation. reports/92233 . 02 • ,r I N t / URLINGro Culvert K 19 3 RM333 _ K .a RM334 L j6 ZONE X i yl a ZONE X I ,I M i Cfi. I ZONE ZONE X X it - STAFFT—` DD Utz tZY Aft BR/DGf UNDfR U\ - CONS7RUCllUN O o Q SOUTNVVFST Z7Ti1 RM338 ----- `. _ STREET.. FtLL, � �� I �.� � � Yp t Z • tiry�� ? •8 // FM 8.40 CURB BREAK 7.50 Y ------------- 1 e. ----- ----10 w — --� I I ----- -- -----79 � r SS M H I TE-19.Oo+ IE-11.26 EXIST. SS MH IE-10.04 - - 30 SS HI r TH A N U E I TE- CH EX CR IE-1 64 8' SAN SEWER RAYM AVENUE S IE-10. - - _ ilIbl IF NO - �- ► '��;�!��` � �11� :fie � '�� AN :OEM ew E� ;7 E �i�� c ► �►► • • r `� '�'�►�-�� 'fir . �� , -r 1 �� ter-� - +..•., �. fli0tN� �- • � f f • IM WOO VIII PAP- � "M `it► f �- �' 7ttr,��i�►��'=��"�� .��►►�`� -. Its. � - ��1 �• � i �� may , KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL LE 3.5.211 SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type 1A rainfall distribution, 24-hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D Cultivated land(t): winter condition 86 91 94 95 low growing brush and grasslands 74 82 89 92 Mountain open areas: 9 g 65 78 85 89 Meadow or pasture: 42 64 76 81 Wood or forest land: undisturbed or older second growth 55 72 81 86 Wood or forest land: young second growth or brush 81 88 92 94 Orchard: with cover crop Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 (3 86 90 fair condition: grass cover on 50% to 75% of the area 77 92 • Gravel roads and parking lots 76 B5 89 9172 82 87 89 Dirt roads and parking lots Impervious surfaces, pavement, roofs, etc. 98 98 98 98100 100 100 100 Open water bodies: lakes, wetlands, ponds, etc. Single Family Residential (2) Dwelling Unit/Gross Acre % Impervious us (3) 1.0 DU/GA Separate curve number 1.5 DU GA 20 shall be selected 0 DU/GA 25 for pervious and 2. DU/GA 30 impervious portion 2.5 34 of the site or basin 3. DU/GA 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 54 7.0 DU/GA 56 Planned unit developments, % impervious condominiums, apartments, must be computed commercial business and industrial areas. (1) For a more detailed description of agrcultural land use curve numbers refer to National Engineering Handbook, Section 4, Hydrology, Chapter 9, August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. 3.5.2-3 11/92 = 2/ 8/96 Bush, Roed & Hitchings, Inc. page I Raymond Street Center John E. Anderson, P.E. C:\92233 ---------- BASIN SUMMARY BASIN ID: bl NAME: 2 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 97 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 .00 inches AREA. . : 4 .97 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 30 . 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres CN. . . . . 98 .00 PEAK RATE: 0 . 30 cfs VOL: 0 . 23 Ac-ft TIME: 490 min BASIN ID: b2 NAME: 10 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .97 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA • PRECIPITATION. . . . : 2.90 inches AREA. . : 4 .97 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 TIME OF CONC. . . . . : 30. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 0.00 Acres CN. . . . . 98.00 PEAK RATE: 0.84 cfs VOL: 0.49 Ac-ft TIME: 480 min BASIN ID: b3 NAME: 25 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 97 Acres BASEFLOWS: 0 .00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 40 inches AREA. . : 4 .97 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 TIME OF CONC. . . . . : 30 . 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 .00 Acres CN. . . . . 98. 00 PEAK RATE: 1 . 21 cfs VOL: 0 .65 Ac-ft TIME: 480 min = 2/ 8/96 Bush, Roed & Hitchings, Inc. page 2 Raymond Street Center John E. Anderson, P.E. C:\92233 ----------- BASIN SUMMARY BASIN ID: b4 NAME: 100 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .97 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 .90 inches AREA. . : 4 .97 Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 30. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 0.00 Acres CN. . . . . 98.00 PEAK RATE: 1 . 60 cfs VOL: 0.81 Ac-ft TIME: 480 min BASIN ID: b5 NAME: 2 year developed SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .97 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 .00 inches AREA. . : 0. 27 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80 .00 TIME OF CONC. . . . . : 16 . 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 4.70 Acres CN. . . . . 98 . 00 PEAK RATE: 1 . 96 cfs VOL: 0. 71 Ac-ft TIME: 480 min BASIN ID: b6 NAME: 10 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 97 Acres BASEFLOWS: 0 .00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0. 27 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16 . 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 4 . 70 Acres CN. . . . . 98 . 00 PEAK RATE: 2 . 93 cfs VOL: 1 . 07 Ac-ft TIME: 480 min t 2/ 8/96 Bush, Roed & Hitchings, Inc. page 3 Raymond Street Center John E. Anderson, P.E. C:\92233 BASIN SUMMARY BASIN ID: b7 NAME: 25 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 97 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 40 inches AREA. . : 0.27 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 80.00 TIME OF CONC. . . . . : 16 . 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0.20 AREA. . : 4 .70 Acres CN. . . . . 98.00 PEAK RATE: 3 . 47 cfs VOL: 1.28 Ac-ft TIME: 480 min BASIN ID: b8 NAME: 100 year existing SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 97 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 .90 inches AREA. . : 0. 27 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80. 00 TIME OF CONC. . . . . : 16. 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0. 20 AREA. . : 4.70 Acres CN. . . . . 98 .00 PEAK RATE: 4 . 02 cfs VOL: 1. 48 Ac-ft TIME: 480 min BASIN ID: b9 NAME: ptwq volume for wetpond SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 97 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 0 . 67 inches AREA. . : 0 . 27 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 80 . 00 TIME OF CONC. . . . . : 16 . 30 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 4 . 70 Acres CN. . . . . 98 . 00 PEAK RATE: 0 . 52 cfs VOL: 0 . 19 Ac-ft TIME: 480 min • I 2/ 8/96 Bush, Roed & Hitchings, Inc. page 2 Raymond Street Center John E. Anderson, P.E. C:\92233 --------------------- HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf-AcFt Acres --------------------------------- 1 0.298 490 10148 cf 4 .97 2 Ke �c�sT;uc� 2 0 .843 480 21207 cf 4 .97 Io ` Z E.x's-T—I 7 3 1 . 206 480 28097 cf 4.97 4 1 .596 480 35348 c 4 .97 goo Xv- ExsT Nc, 5 1.955 480 30824 cf 4 .97 = "0Z DcvEu r� C 0 Y2 r7= /EL7^=-,� 8 4 .016 480 64455 cf 4.97 0o Ue ^:vE oD5r7 9 0.518 480 8116 cf 4.97 ��wW .roRr�t 11 0 .151 1470 21877 cf 4.97 Vz-Z--2 o�tin oar,=ww 12 - 0.40-2-1-4- —Z9775 cf 4 .97 Tlro/ZS n 13 0.590 920 38594 cf 4 . 97 oUTc1-01AJ - f��Pr�2�f✓�6t�L"C OTr ��SNEtz� �5 � ro�r.� �Llu�Q.E M ENZS ', !Z. :-f i; lJT i 2/ 8/96 Bush, Roed & Hitchings, Inc. page 3 • John E. Anderson, P.E. Raymond Street Center C:\92233 --------------------------------------------------------------------- --------------------------------------------------------------------- STORAGE STRUCTURE LIST STORAGE LIST ID No. 1 Description: detention pond too YsRrz = 13 CpZ C • ��Qu��2ED '��ET �� /ol.urv�E, _ ��D -�� — 8 �I Co G'F i 2/ 8/96 Bush, Roed & Hitchings, Inc. page 4 Raymond Street Center John E. Anderson, P.E. C:\92233 STAGE STORAGE TABLE CUSTOM STORAGE ID No. 1 Description: detention pond STAGE <----STORAGE----> STAGE <----STORAGE----> STAGE <----STO (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- 11.00 0.0000 0.0000 12. 50 21443 0.4923 14.00 4678 11.50 6797 0 .1560 13 .00 29293 0.6725 14 . 50 5638 12 .00 13594 0. 3121 13 . 50 38037 0. 8732 15.00 6598 • 2/ 8/96 Bush, Roed & Hitchings, Inc. page 5 Raymond Street Center John E. Anderson, P.E. C:\92233 DISCHARGE STRUCTURE LIST MULTIPLE ORIFICE ID No. 1 Description: control structure Outlet Elev: 11.00 Elev: 11. 00 ft Orifice Diameter: 1.8800 in. Elev: 13 .55 ft Orifice 2 Diameter: 8 . 0000 in. I t 2/ 8/96 Bush, Roed & Hitchings, Inc. page 6 Raymond Street Center John E. Anderson, P.E. C:\92233 LEVEL POOL TABLE SUMMARY MATCH INFLOW ST DI <-PEAK-> STORAGE <--------DESCRIPTION---------> (cfs) (cfs) id id <-STAGE> id VOL (cf) ---------------- 1/2-2yr ex. @ 10 yr . . . . . . . . . . 0. 30 2.93 1 1 13.47 11 374 25 yr ex. @ 25 dev . . . . . . . . . . . 1.21 3 . 47 1 1 13.56 12 391 100 yr ex. @ 100 d . . . . . . . . . . . 1.60 4 .02 1 1 13.62 13 400 • • EROSION CONTROL CALCULATIONS FOR RAYMOND CENTER NW CORNER SOUTHWEST 19TH STREET AND RAYMOND AVENUE SOUTHWEST RENTON, WASHINGTON BY • BUSH, ROED & HITCHINGS, INC. 2009 MINOR AVENUE EAST SEATTLE, WA 98102 (206) 323-4144 BRH JOB NO. 92233 . 02 MARCH 22 , 1995 CONTACT PERSON: JOHN E. ANDERSON, P.E. JOB BUSH, ROED & HTTCHINGS,INC. q Z��- 0 2 P aY�o►Jfl c.6.�T�r�_- CIVIL ENGINEERS & LAND SURVEYORS SHEET NO. of 2009 Minor Avenue East CALCULATED BY DATE Seattle,WA 98102 • 1�� (206)323-4144 CHECKED BY DATE B (206)323-7135 ' Fax SCALE _..... c.A t,,e J A T 1-zi,� t..1�>'L� Lprn►oJ TE,� . J S i tit C:� T H E U P t7 r4 E-- -V Q J C7 F Cmµ✓�P i E�L Fruor-, T 14;�-- ►-iJ LFAc—.G TF-'E� Ex I ST�►J c, s� r� �_S ;c,�ja-✓z(r-.-J>-L--e U►Jt7.`v6-oPV T Arn T 15i2"(3C7--) WLrc,A Tti-4� 6(2cio� /-SEd�ME►JT �o� PC►.l P PES 1 Cati 5 V f -k6p-c-S ►.► co 3 s�PEvLv� +�ASI►JS . ( � AIT�c-H-�� M/JP FOB �ipiL,S� IDA >i J A.Q.t P� P-,A s �.IORT�� 2 ,53 ce ,►-� �l � C A "SOT A Dt,--ir4,jt>E0 t A �2o../i rDC +� • 10 tz— '6: F3�45 ►.� . viaoua lOFI is�or fM4110S1 ®.rc.Nobs.Jim 01471 E.ar EEW tau FKE I4*n5'W I 1/22/95 Bush . Roed & Hitchinas . Inc. page 1 Winmar John E. Anderson . P.E. storm disk-92233 HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf-AcFt Acres 1 0.298 490 10148 cf 4 .97 2 0.843 480 21207 cf 4.97 3 1 . 206 480 28097 cf 4 . 97 4 1 . 596 480 35348 cf 4.97 5 1 .955 480 30824 cf 4 .97 6 2 . 932 480 46683 cf 4.97 7 3 . 474 480 55555 cf 4 . 97 8 4 .016 480 64455 cf 4 . 97 9 0. 515 480 8068 cf 4 . 97 11 0.129 1470 19342 cf 4.97 12 0. 397 1450 26581 cf 4.97 13 0. 504 1030 35290 cf 4.97 14 0. 281 480 6157 cf 1 . 65 EST g�►s�►J 15 0.431 480 9441 cf 2. 53 ►aog-T14 2,#s►►J 16 0 . 511 480 11194 cf 3 .00 JEST e**,6uA • KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL '5 4.5.1 SEDIMENT TRAP Code: ST Symbol: Purpose To remove sediment from runoff originating from disturbed areas of the site. Sediment traps are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually only result in a small reduction in turbidity. Conditions of Use 1. A sediment trap shall be used where the contributing drainage area is 3 acres or less. Design and Installation Specifications 1. See Figure 5.4.5.11A for detail. 2. If permanent runoff control facilities are part of the project, they should be used for sediment retention (see the introduction to this section). 3. To determine the trap geometry, first calculate the design surface area (SA) of the trap, measured at the invert of the weir . Use the following equation: SA = FS(Q2/Vs), where: f 02 = Design inflow based on the peak discharge from the developed 2-year, 24-hour design storm from the contributing drainage area as computed in the hydrologic analysis. The 10-year, 24-hour design storm shall be used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required, the rational method may be used (Section 4.3.3). Vs = The settling velocity of the soil particle of interest. The 0.02 mm (medium silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (vs) of 0.00096 ft/sec. FS = A factor of safety of 2 to account for non-ideal settling. Therefore, the equation for computing surface area becomes: SA =2 x Q2/0.00096 or 2080 square feet per cfs of inflow NOTE: Even if permanent facilities are used, they must still have a surface area that is at least as large as that derived from the above formula. If they do not, the pond must be enlarged. 4. To aid in determining sediment depth, all traps shall have a staff gauge with a prominent mark 1 foot above the bottom of the trap. 5.4.5.1-1 11194 KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL FIGURE 5.4.5.1A SEDIMENT TRAP SURFACE AREA DETERMINED 4' MIN. AT TOP OF WEIR iL. T - V MIN. OVERFLOW Jy IT 1' MIN. �4 1' MIN. FLAT BOTTOM RIPRAP 3/4"-1.5" 4" ROCK WASHED GRAVE\2-- GEOTEXTILE NOTE: TRAP MAY BE FORMED BY BERM OR BY DISCHARGE TO STABILIZED PARTIAL OR COMPLETE EXCAVATION CONVEYANCE. OUTLET OR LEVEL SPREADER CROSS-SECTION 6' MIN. - - TT _III-III-III-III-I I-II V MIN. DEPTH OVERFLOW SPILLWAY -III-III-III-III-III-I Ii-Tr=1 i�lil�lil-I I E-1 '= MIN. 1' DEPTH NATIVE SOIL OR �rI I ti• j 2"-4" ROCK COMPACTED BACKFILL MIN. 1 DEPTH 3/4 GEOTEXTILE (��{I I-III-I I�l 11=I I{=1 I I-I I�1 11= WASHED GRAVEL I l-III=l I�I I I=I I l-1 I�1 11=1 I�1 TRAP OUTLET Maintenance Standards 1. Sediment shall be removed from the trap when it reaches 1 foot in depth. 2. Any damage io the trap embankments or slopes shall be repaired. 5.4.5.2 SEDIMENT POND Code: SP Symbol: Purpose To remove sediment from runoff originating from disturbed areas of the site. Sediment traps are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually reduce turbidity only slightly. Conditions of Use 1. A sediment pond shall be used where the contributing drainage area is 3 acres or more. 5.4.5.2-1 11/94 BUSH,ROED& HIMUNGS,INC. roe CIVIL ENGINEERS& LAND SURVEYORS SHEET No. of 2009 Minor Avenue East CALCULATED BY DATE Seattle,WA 98102 f� (206)323-4144 CHECKED BY DATE B (206)323-7135 • Fax SCALE dt'c t3 ....................:........... Sll 0. 00®gam _ ................ 09, _ .._.........._ ......... �ClS I ��45,►.� = 2 ,Zol 0 .000 ( ....... NOW 20M pop W loMI(FWM®.BC..6.0m 014711@ 0ift MOTE TOLL T1e 14062254=